1. Field of the Invention
In air conditioning systems wherein air is delivered through ducts, there is often a need to measure the average temperature of the air passing through the duct. If a single temperature responsive element is used in one portion of the duct, the air stratification or mixing of the air is not always sufficient that the temperature with a single positioned temperature responsive element provides a true temperature of the total air passing through the duct.
2. Description of the Prior Art
Averaging temperature responsive apparatus for use in an air conditioning duct have had various forms. For many years a wire wound Balco temperature responsive resistance element where the wire is wound on a long support element which when inserted into the side of a duct would extend transversely across the duct to be impinged upon by the air flowing through the duct and thus provide an average temperature reading of the air. Such elements were not only expensive to manufacture but in many cases did not provide a true averaging temperature measurement.
Another form of averaging temperature responsive apparatus makes use of a tubular air conduit which is long enough to extend transversely across the duct. The conduit has either a continuous slit opening or a plurality of inlet openings on the upstream side and at least one opening on the downstream side. Positioned adjacent the downstream opening is a temperature responsive element so that as the air entering the upstream openings passes through the conduit and mixes, the temperature of the air as sensed by the temperature responsive element provides an average temperature of the air in the duct. Such prior art devices depend on pressure differential to promote air movement down the tube to the sensing element.